Forerunners of communist ideas existed in antiquity and particularly in the 18th and early 19th century France, with thinkers such as Jean-Jacques Rousseau and the more radical Gracchus Babeuf. Radical egalitarianism then emerged as a significant political power in the first half of 19th century in Western Europe. In the world shaped by the Industrial Revolution and the French Revolution, the newly established political left included many various political and intellectual movements, which are the direct ancestors of today's communism and socialism – these two then newly minted words were almost interchangeable at the time – and of anarchism or anarcho-communism.

Communism in the Marxist sense refers to a classless, stateless, and oppression-free society where decisions on what to produce and what policies to pursue are made directly and democratically, allowing every member of society to participate in the decision-making process in both the political and economic spheres of life. Some "revisionist" Marxists of the following generations, henceforth known as reformists or social democrats, have slowly drifted away from the revolutionary views of Marx, instead arguing for a gradual parliamentary road to socialism; other communists, such as Rosa Luxemburg and Vladimir Lenin, continued to agitate and argue for world revolution.

The Bolsheviks, led by Vladimir Lenin, were brought to power by the Russian Revolution of 1917, where the Tsarist regime disrupted by World War I was smashed by the world's first workers revolution. After years of civil war (1917–1921), international isolation, erosion of the soviets (workers and peasants' councils) and internal struggle within the Bolshevik leadership, the Soviet Union was founded (1922). Lenin died after a second stroke in 1924, and despite of his warnings was succeeded by Joseph Stalin.

Once in power, Stalin carried out multiple purges of dissidents and left communists/opposition, particularly of those around Leon Trotsky, and established the character of Communism as the totalitarian ideology it is most commonly known as and referred to today. The Soviet Union emerged as a new global superpower on the victorious side of World War II. In the five years after the World War, Communist regimes were established in many states of Central and Eastern Europe and in China. Communism began to spread its influence in the Third World while continuing to be a significant political force in many Western countries.

International relations between the Soviet Bloc and the West, led by USA, quickly worsened after the end of the war and the Cold War began, a continuing state of conflict, tension and competition between the United States and the Soviet Union and those countries' respective allies. The "Iron curtain" between West and East then divided Europe and world from the mid-1940s to the early 1990s. Despite many Communist successes like the victorious Vietnam War (1959-1975) or the first human spaceflight (1961), the Communist regimes were ultimately unable to keep up with their Western rivals. People under Communist regimes showed their discontent in events like the Hungarian Revolution of 1956, Prague Spring of 1968 or Polish Solidarity movement in early 1980s, most of which were ironically led by or included masses of workers.

Criticism of the idea of private property continued into the Age of Enlightenment in the 18th century, through such thinkers as Jean Jacques Rousseau. Later, following the upheaval of the French Revolution, communism emerged as a political doctrine.[8]Gracchus Babeuf, in particular, espoused the goals of common ownership of land and total economic and political equality among citizens.

During the early development of the political left in the first decades of 19th century, the germs of communism – together with those of socialism, Christian utopianism, anarchism, trade-unionism, and feminism – differentiated and were theoretically examined. The term "communism" was probably coined by the French utopist Étienne Cabet for his communitarian social movement in 1839. In the following year 1840 the British leftist John Goodwyn Barmby used this term for Babeuf's teachings. The word "socialism" came in use about 1840 and both terms were largely interchangeable at the time; the difference between the two terms was largely regional and cultural: In continental Europe "communism" was thought to be more radical and secular than socialism, while British revolutionaries preferred "socialism".[9]

The early socialist movement, rather undifferentiated at the time, concentrated in the most industrialised European countries. In France with its revolutionary tradition lived Henri de Saint-Simon, whose circle coined the term "exploitation of man by man"; Charles Fourier, the inventor of the word "feminism" and a propagator of communist communities; and Louis Auguste Blanqui, author of the term "dictatorship of the proletariat", who spent most of his life in prisons for his revolutionary actions. France saw also activities of early anarchists Pierre-Joseph Proudhon, who asserted that "Property is theft!", and the Russian nobleman Mikhail Alexandrovich Bakunin.

In Great Britain, the Chartist movement, named after the People's Charter published in 1838, demanded the equal civil right to vote for all men, including the lower classes. Among early English social reformers was the utopianRobert Owen, the founder of the cooperative movement and of the utopian community of New Harmony. Founded in the U.S. state of Indiana in 1825, New Harmony collapsed after four years over internal quarrels, much like other similar undertakings.[10]

Marxism, initially developed by German revolutionary philosophers Karl Marx and Friedrich Engels from 1840s into the 1890s, became the principal form of socialist thought during this time, and with few exceptions, it remained in this position well until the 1970s. Most influential leftist and socially critical theories either develop Marxism further (e.g., social democracy, Leninism, Maoism and Trotskyism), or completely drop Marxist ideology and do not set the creation of classless society as their aim (e.g., the modern feminism, New Labour, environmentalism). Therefore the words Marxism and communism are usually understood as synonymous.

Marx and Engels considered capitalism to be a system based on relentless competition for profit, or surplus value as they put it, among capitalists and capitalist states. In his labour theory of value, Marx argued that this becomes possible by the exploitation and the oppression of workers. According to Marx, the main characteristic of human life in a class society is alienation, while communism entails the full realisation of human freedom.[12] Marx here follows Georg Wilhelm Friedrich Hegel in conceiving freedom not merely as an absence of restraints but as action with content.[13] Marx believed that communism would give people the power to appropriate the fruits of their labor while preventing them from exploiting others. Whereas for Hegel the unfolding of this ethical life in history is mainly driven by the realm of ideas, for Marx, communism emerged from material forces, particularly the development of the means of production.[13]

Marxists hold that due to the innate antagonism and class conflict between labour and capital, the inevitable process of revolutionary struggle can result in victory for the proletariat, or the workers, and the establishment of a communist society in which private ownership is abolished over time and the means of production and subsistence become the collective property of society. Marx himself wrote little about life under communism, giving only the most general indication as to what constituted a communist society. The German Ideology (1845) was one of Marx's few writings to elaborate on the communist future:

"In communist society, where nobody has one exclusive sphere of activity but each can become accomplished in any branch he wishes, society regulates the general production and thus makes it possible for me to do one thing today and another tomorrow, to hunt in the morning, fish in the afternoon, rear cattle in the evening, criticise after dinner, just as I have a mind, without ever becoming hunter, fisherman, herdsman or critic."[14]

In the late 19th century, the terms "socialism" and "communism" were often used interchangeably. However, Marx and Engels argued that communism would not emerge from capitalism in a fully developed state, but would pass through a lower phase in which productive property was owned in common but people would be allowed to take from the social wealth only to the extent of their contribution to the production of that wealth. As the masses of the people begin to overcome their alienation and replace competition with social cooperation, this "lower phase" would eventually evolve into a "higher phase" in which the antithesis between mental and physical labour has disappeared, people enjoy their work, and goods are produced in abundance, allowing people to freely take according to their needs. Lenin frequently used the term "socialism" to refer to Marx and Engels' "lower phase" of communism and used the term "communism" interchangeably with Marx and Engels' "higher phase" of communism.

The first Marxist international organisation was the Communist League. It was founded originally as the League of the Just by German workers in Paris in 1836. This was initially a utopian socialist and Christian communist grouping devoted to the ideas of Gracchus Babeuf. The League of the Just participated in the Blanquist uprising of May 1839 in Paris.[15] Thereafter expelled from France, the League of the Just moved to London where by 1847 numbered about 1,000. Wilhelm Weitling's 1842 book, Guarantees of Harmony and Freedom, which criticised private property and bourgeois society, was one of the bases of its social theory. The Communist League was created in London in June 1847 out of a merger of the League of the Just and of the fifteen-man Communist Correspondence Committee of Bruxelles, headed by Karl Marx.[16] The birth conference was attended by Friedrich Engels, who convinced the League to change its motto from All men are brethren[17] to Karl Marx's phrase, Working men of all countries, unite!. The Communist League held a second congress, also in London, in November and December 1847. Both Marx and Engels attended, and they were mandated to draw up a manifesto for the organisation. This became the famous The Communist Manifesto. The League was ended formally in 1852.

In 1864 in a workmen's meeting held in Saint Martin's Hall, London there was founded the International Workingmen's Association (IWA), better known as the First International. It was an international socialist organisation which aimed at uniting a variety of different left-wing political groups and trade union organisations that were committed to the working class and class struggle. At its founding, it was an alliance of people from diverse groups, besides Marxists it included French Mutualists, Blanquists, English Owenites, Italian republicans, such American proponents of individualist anarchism as Stephen Pearl Andrews and William B. Greene, followers of Mazzini, and other socialists of various persuasions. Due to the wide variety of philosophies present in the First International, there was conflict from the start. The first objections to Marx's came from the Mutualists who opposed communism and statism. However, shortly after Mikhail Bakunin and his followers (called Collectivists while in the International) joined in 1868, the First International became polarised into two camps, with Marx and Bakunin as their respective figureheads. Perhaps the clearest differences between the groups emerged over their proposed strategies for achieving their visions of socialism. The anarchists grouped around Bakunin favoured (in Kropotkin's words) "direct economical struggle against capitalism, without interfering in the political parliamentary agitation." Marxist thinking, at that time, focused on parliamentary activity. For example, when the new German Empire of 1871 introduced manhood suffrage, many German socialists became active in the Marxist Social Democratic Party of Germany.

In 1872, the conflict in the First International climaxed with a final split between the two groups at the Hague Congress. This clash is often cited as the origin of the long-running conflict between anarchists and Marxists. From then on, the Marxist and anarchist currents of socialism had distinct organisations, at various points including rival 'internationals'. In 1872, the organisation was relocated to New York City. The First International disbanded four years later, at the 1876 Philadelphia conference.

In the last years of the First International there was a short-lived but important first attempt of socialists to seize power, the Paris Commune, a government that briefly ruled Paris, from March 28 to May 28, 1871. It existed before the final split between anarchists and socialists had taken place, and therefore it is hailed by both groups as the first assumption of power by the working class. Debates over the policies and outcome of the Commune contributed to the break between those two political groups.

Although mostly Marxist, this loose federation of the world’s socialist parties included both openly reformist organisations that saw a gradual implementation of reforms to capitalism as the way to achieve socialism (forerunners of today's social democrats), and revolutionary socialist parties that saw the need to smash the capitalist state structure through a mass workers' revolution in order to create a communist society (communists in the sense of the 20th century).

In Russia, the 1917 October Revolution was the first time any mass party with an avowedly Marxist ideology, in this case the Bolshevik Party, seized state power. The assumption of state power by the Bolshevik-led workers' Soviets generated some practical and theoretical debate within the Marxist movement. Marx had predicted that socialism and communism would most likely be built upon foundations laid by capitalism in the most advanced capitalist countries such as Germany and Britain. Russia, however, was at the time one of the poorest and most industrially backward countries in Europe with an enormous, largely illiterate peasantry and a minority of industrial workers. Marx, however, had explicitly stated that Russia might be able to skip the stage of bourgeoisie capitalism.[20], an idea further developed by Leon Trotsky known as the theory of permanent revolution. Other socialists also believed that a Russian revolution could be the precursor of workers' revolutions in the West, drawing on the volatile and pre-revolutionary climate in Germany, Italy and Austria.

The Mensheviks, however, opposed the Bolshevik's notion of socialist revolution before capitalism was fully developed in Russia. The Bolsheviks' successful rise to power was partially based upon their slogans of "Peace, bread, and land" and "All power to the Soviets!", slogans which tapped the massive public desire for an end to Russian involvement in the First World War, the peasants' demand for land reform, and popular support for the Soviets.

Once in power, the Bolsheviks immediately withdrew Russia from the First World War, established workers' control in the factories, legalised divorce, installed universal suffrage, granted freedom and self-determination to national minorities, carried out major land reforms in the interest of poor peasants, initiated mass literacy campaigns, assisted the restoration of oppressed religious minorities, decriminalised homosexuality, separated the church and the state, began the task of eliminating homelessness and "freed" women from the burden of housework by setting up communal kitchens, laundries and free nurseries for children. Many of their progressive policies such as the decriminalisation of homosexuality were however reverted once Stalin assumed power.

The usage of the terms "communism" and "socialism" began to shift after 1917, when the Bolsheviks changed their name to the Communist Party and devoted the power of the state to the implementation of socialist policies, in line with what is today referred to as Leninism. Lenin established the Third International (Comintern) in 1919 in order to unite the efforts of the world's communist parties in their fight against capitalism, and in 1920 issued the Twenty-one Conditions, which included democratic centralism, to all European socialist parties willing to adhere. In France, for example, the majority of the SFIO socialist party split in 1921 to form the French Communist Party (French Section of the Communist International). Henceforth, the term "Communist" was applied to the parties founded under the umbrella of the Comintern. Their program called for the uniting of workers of the world for workers' revolution, which would be followed by the establishment of a democratic and temporary dictatorship of the proletariat, as well as the development of a socialist economy, ultimately leading to the withering away of the state and the development of a harmonious classless society, based on cooperation instead of market competition.

During the Russian Civil War (1918–1922), the Bolsheviks nationalised all means of production and imposed the policy of war communism, which put factories and railroads under government control, collected and rationed food, and introduced some temporary bourgeois management of industry. After three years of war and the 1921 Kronstadt rebellion and in light of the failure of the Russian Revolution to spread to the rest of Europe, Lenin declared the New Economic Policy (NEP) in 1921, which was to give a "limited place for a limited time to capitalism." The NEP lasted until 1928, when Joseph Stalin seized party leadership, and the introduction of the first Five Year Plan spelled the end of it. Following the Russian Civil War, the Bolsheviks formed in 1922 the Union of Soviet Socialist Republics (USSR), or Soviet Union, from the former Russian Empire.

Stalinism usually defines the style of a government rather than an ideology. The ideology was Marxism-Leninism, reflecting that Stalin prided himself on the claim of maintaining the legacy of Lenin as a founding father of the Soviet Union and the future Socialist world. Stalinism is an interpretation of their ideas, and a certain political regime claiming to apply those ideas in ways fitting the changing needs of society, as with the transition from "socialism at a snail's pace" in the mid-twenties to the rapid industrialisation of the Five-Year Plans. Sometimes, although rarely, the compound terms "Marxism-Leninism-Stalinism" (used by the BrazilianMR-8), or teachings of Marx/Engels/Lenin/Stalin, are used to show the alleged heritage and succession. Simultaneously, however, many Marxists and Leninists view Stalinism as a perversion of their ideas; Trotskyists, in particular, are virulently anti-Stalinist, considering Stalin a counter-revolutionary.

At the end of the 1920s Stalin launched a wave of radical, and often brutal, economic policies, which completely overhauled the industrial and agricultural face of the Soviet Union. This came to be known as the Great Turn as Russia turned away from the quasi-capitalist New Economic Policy. The NEP had been implemented by Lenin in order to ensure the survival of the state following isolation and seven years of war (1914-1921, World War I from 1914 to 1917, and the subsequent Civil War) and had rebuilt Soviet production to its 1913 levels. It "modernized the Soviet Union, transforming a peasant society into an industrial state with a literate population and a remarkable scientific superstructure",[22] but at the expenses of forced collectivisation, famine and terror.[23]

Communist states such as the Soviet Union and China succeeded in becoming industrial and technological powers, challenging the capitalists' powers in the arms race and space race and in military conflicts.

The split between Communist and capitalist worlds resulted in the Cold War, an continuing state of conflict, tension and competition that existed primarily between the United States and the Soviet Union and those countries' respective allies from the mid-1940s to the early 1990s. Throughout this period, the conflict was expressed through military coalitions, support for various dictatorships, espionage, weapons development, invasions, propaganda, and competitive technological development, which included the space race. The conflict included costly defense spending, a massive conventional and nucleararms race, and numerous proxy wars; the two superpowers never fought one another directly.

The Soviet Union created an Eastern Bloc of countries that it occupied, annexing some as Soviet Socialist Republics and maintaining others as Satellite states that would later form the Warsaw Pact. The United States and various western European countries began a policy of "containment" of Communism and forged many alliances to this end, including later NATO. In the Third world the Soviet Union fostered Communist revolutionary movements, which the United States and many of its allies opposed and, in some cases, attempted to "rollback". Many countries were prompted to align themselves with the countries that would later either form NATO or the Warsaw Pact. The Cold War saw periods of both heightened tension and relative calm as both sides sought détente. Direct military attacks on adversaries were deterred by the potential for mutual assured destruction using deliverable nuclear weapons.

The relations between the Soviet Union and its satellites were described by the so-called Brezhnev Doctrine which was announced to justify the Soviet invasion of Czechoslovakia in August 1968 to terminate the Prague Spring, an attack similar to earlier Soviet military interventions, such as the invasion of Hungary in 1956. These interventions were meant to put an end to liberalisation efforts and uprisings that had the potential to compromise Soviet hegemony inside the Eastern Bloc, which was considered by the Soviets to be an essential defensive and strategic buffer in case hostilities with the West were to break out. It meant that limited independence of Communist parties was allowed, but no country would be allowed to leave the Warsaw Pact, disturb a nation's Communist party's monopoly on power, or in any way compromise the strength of the Eastern Bloc. Implicit in this doctrine was that the leadership of the Soviet Union reserved, for itself, the right to define "socialism" and "capitalism". The principles of the doctrine were so broad that the Soviet Union even used it to justify its military intervention in the non-Warsaw Pact nation of Afghanistan in 1979.

The Cold War drew to a close in the late 1980s and the early 1990s. The United States under President Ronald Reagan increased diplomatic, military, and economic pressure on the Soviet Union, which was already suffering from severe economic stagnation. In the second half of the 1980s, newly appointed Soviet leader Mikhail Gorbachev introduced the perestroika and glasnost reforms.

The communist ideology in its Marxist stream is still alive and well. Trotskyists amongst other Marxists continue to describe themselves as socialist and communist interchangeably. Many of them hold that since the Soviet Union after the rise of Stalin to power was nothing more than a state capitalist country, its demise means nothing more than the failure of one style of capitalist economic organisation. Although small in numbers, Marxist socialists and communists continue to build their ranks in many countries such as the Socialist Workers Party (SWP) in Britain, International Socialist Organization (ISO) in the US and the New Anticapitalist Party in France.

Marxist-Leninist stream of thought on the other hand has been damaged and further discredited by the collapse of the Soviet Union. This has meant that many Communist parties worldwide have lost mass membership and shifted to the right, adopting reformist and free market politics. Some Communist states such as the People's Republic of China and other Asian Communist states and Cuba, though have proven resistant. The Chinese version of reforms concentrated on support of market forces while effectively prohibiting Western-style freedoms and human rights and was able to both maintain the dominant role of the Communist Party and to quickly expand and modernise the economy. This, however, has created its own internal tensions and contradictions—as the Chinese working class has massively expanded in numbers, it has begun to do so in class consciousness and class demands, all in odds with the wishes of the State establishment.

The People's Republic of China has reassessed many aspects of the Maoist legacy; and the People's Republic of China, Laos, Vietnam, and, to a far lesser degree, Cuba have reduced centralised state planning of the economy in order to stimulate growth. The People's Republic of China runs Special Economic Zones dedicated to market-oriented enterprise, free from central government control. As of 2005, anywhere between 33%[30] (People's Daily Online 2005) to 70%[31] (BusinessWeek, 2005) of GDP in 2005, while the OECD estimate is over 50%[32] of China's GDP came from the private sector, a figure that might be even larger when taking into account the Chengbao system. As a result, many observers argue that China has become an entirely free-market economy[33] and despite the name of the Communist Party of China has de facto ceased pursuing the development and establishment of a Communist society. Several other Communist-led states have also attempted to implement market-based socialist reforms, including Vietnam, which slowly implemented reforms that transformed the Vietnamese economy into what is officially term a Socialist-oriented market economy.

↑E. Szafarz, "The Legal Framework for Political Cooperation in Europe" in The Changing Political Structure of Europe: Aspects of International Law, Martinus Nijhoff Publishers. ISBN 0-7923-1379-8. p.221.